Studies are being carried out on 2 cell lines in culture. C-1300 neuroblastoma cells, and C-6 astrocytoma cells are used to investigate differences, if any between the metabolism of cells of glial and neural origin. The regulation of cyclic AMP and cyclic GMP concentrations in the cells, and the fluctuation of these compounds in response to hormones and/or drugs is under investigation. C-6 cells respond to norepinephrine, and C-1300 cells respond to prostaglandin E, in that adenyl cyclase is activated and cyclic AMP concentrations increase. Both cell lines have phosphodiesterase activities which are specific for the degradation of the 2 cyclic nucleotides, and both enzyme activities can be induced. The effect of thiamine deficiency or metabolites and thiamine-linked enzymes has been investigated in both cell lines. A study of the effects of glucose deprivation and/or anaerobiasis has also been undertaken.